Update AWS Lambda for DB snapshots to secondary account

> Dear Amazon RDS Customer
We have noticed that since 1 October 2020 you are generating DescribeDBSnapshot and DescribeDBInstances calls in the US-EAST-1 region that are failing with a 500 error because of incorrect filter usage.
The calls are being requested with the following parameters:
{"filters":[{"name":"db-snapshot-id"}],"includeShared":false,"includePublic":false,"dbinstanceIdentifier":"notification-alpha-canada-ca-enc"}
In order to make sure your calls don't fail, we recommend that refer to our documentation for filter usage [1] and modify the parameters accordingly.
For the fastest feedback and best user experience, we also recommend that you upgrade to the latest NodeJS SDK and enable client side validations.
If you have any further questions or require any guidance, please do not hesitate to contact the AWS Support team. We would be happy to help. We are available on the community forums or by contacting AWS Premium Support [2].
Sincerely,
The Amazon RDS Team

This happened due to an AWS API change. Max has disabled the lambda in the short term, so we are not currently getting backups to a secondary location. Regular backups inside the same AWS account are not affected.

To do:
- Update this
- Figure out how to alarm if this stops happening - we didn't know this was broken for 19 days

https://console.aws.amazon.com/lambda/home?region=us-east-1#/functions/rds-snapshot-backup?tab=configuration

https://github.com/cds-snc/aws-rds-cross-account-backup/tree/master/rds-backup